Radiation-sensitive resin composition with admixtures of O-quinone diazide and acid esters having nitrobenzyl or cyanobenzyl group

ABSTRACT

A radiation-sensitive resin composition comprising a quinonediazide-type radiation-sensitive resin and a compound generating an acid upon irradiation. Said radiation-sensitive resin composition can be used as a resist suitable for dry development by plasma etching and enables one to obtain an etching image having high precision with high reproducibility at a high degree of resolution and selectivity.

This invention relates to a radiation-sensitive resin composition and,more particularly, to a radiation-sensitive resin composition which canbe used as a resist suitable for dry development by plasma etching.

Conventionally, in processes for producing semiconductor elements suchas ICs and LSIs, a photolithographic method has been employed, in whicha radiation-sensitive resin composition, such as a negative-typephotoresist prepared by blending a polyisoprene-cyclized rubber and abisazide or a positive-type photoresist obtained by mixing a novolakresin and a quinonediazide-type compound, is coated on a substrate to beprocessed, exposed to g-line (wave length: 436 nm) or i-line (wavelength: 365 nm) from a mercury lamp, and developed by a developingsolution to obtain an intended pattern.

In recent years, however, the size of LSIs becomes extremely small,requiring the minimum size of a pattern of less than 1 μm to be formedon a substrate. The problem encountered in forming a pattern with thisrange of the size is that it is difficult to produce a sufficientresolution due to adverse effects of light reflection in the exposedresist layer and a shallow depth of focus in the exposure system, whenthe conventional photolithographic method is used. This is speciallytrue in case where the substrate has a highly reflective topography.

In order to avoid this type of problem, a method is known to produce aresist pattern by a photolithographic method wherein the development iseffected by etching in anisotropic gas plasma such as oxygen plasma,instead of using wet development.

For example, EP-A-0,184,567 discloses a method for producing a desirednegative pattern via. the following steps. A layer of aradiation-sensitive resin, which is either a mixture of a polymericcompound and a photo-active compound or a polymeric compound to which aphoto-active compound is bound, is first coated on a substrate. Thecharacteristic of this layer is such that when the area to be irradiatedis exposed to visible or ultraviolet light, a silicon compound isselectively diffused in the irradiated area. Only selected areas of thislayer of the radiation-sensitive resin are then exposed to visible orultraviolet light through a mask. This irradiated radiation-sensitiveresin layer is treated with a silicon compound so that it may beselectively diffused into the irradiated area and react with the polymerof this area. Finally, the layer of the radiation-sensitive resin thustreated is subjected to dry development by means of anisotropic plasmaetching to selectively eliminate the unirradiated area thus obtaining adesired pattern.

As a radiation-sensitive resin to be used in this process,EP-A-0,184,567 discloses a polymer mixed or condensed withquinonediazide. In this type of radiation-sensitive resin, however, thediffusion of and reaction with a silicon compound takes place even at anunirradiated area, and it is difficult to produce a pattern by means ofthe oxygen plasma etching without producing residues at unirradiatedareas. This requires the two-step plasma etching development, i.e., thefirst etching with an oxygen plasma containing a fluorine-containinggas, and the second etching with a pure oxygen plasma, thus making thedry development process very complicated.

The present inventors have conducted extensive studies in order to solvethese problems, and discovered a radiation-sensitive resin composition,which, when used as a resist for dry development and subjected toetching with an oxygen plasma, can provide a high degree of resolutionand selectivity.

According to this invention, there is provided a radiation-sensitiveresin composition comprising a quinonediazide-type radiation-sensitiveresin and a compound generating an acid upon irradiation (said compoundis hereinafter referred to as "photoacid").

The quinonediazide-type radiation-sensitive resin (hereinafter referredto simply as "radiation-sensitive resin") used in this inventionincludes a condensate of a quinonediazide compound with analkali-soluble resin, a mixture of a quinonediazide compound and analkali-soluble resin, and the like. These may be used alone or incombination of two or more.

The alkali-soluble resin to be used may be a novolak resin havinghydroxyl groups, a hydroxystyrene resin or the like. These may be usedalone or in combination of two or more.

In this specification, the term "hydroxystyrene resin" means a polymeror copolymer, at least part of which is composed of hydroxystyreneand/or a hydroxystyrene derivative, and the hydroxystyrene derivativeincludes alkyl-substituted hydroxystyrenes and the like.

The novolak resin having hydroxyl groups can be synthesized bycondensing a hydroxy aromatic compound with an aldehyde compound.

Examples of the hydroxy aromatic compound to be used in the synthesis ofa novolak resin having hydroxyl groups are hydroxynaphthalenes such as1-naphthol, 2-methyl-1-naphthol, 4-methoxy-1-naphthol,4-ethoxy-1-naphthol, 4-propoxy-1-naphthol, 4-butoxy-1-naphthol,5-methyl-1-naphthol, 2-ethyl-1-naphthol, 2-propyl-1-naphthol,2-butyl-1-naphthol and the like; and phenols such as phenol, alkylphenols (cresol, ethylphenol, butylphenol, xylenol, trimethylphenol andthe like), phenylphenol and the like.

These hydroxy aromatic compounds can be used either along or incombination of two or more.

The aldehyde to be employed includes formaldehyde, paraformaldehyde,acetaldehyde, propylaldehyde, benzaldehyde, phenylacetaldehyde,α-phenylpropylaldehyde, β-phenylpropylaldehyde, o-chlorobenzaldehyde,m-chlorobenzaldehyde, p-chlorobrnzaldehyde, o-methylbenzaldehyde,m-methylbenzaldehyde, p-methylbenzaldehyde, p-ethylbenzaldehyde,p-n-butylbenzaldehyde and the like.

In this reaction, the aldehyde is used in an amount usually of 0.7-3mols, preferably 1.1-2 mols, per mol of the hydroxy aromatic compound.

Either an inorganic acid such as hydrochloric acid, nitric acid orsulfuric acid, or an organic acid such as formic acid, oxalic acid oracetic acid can be employed as a catalyst.

The amount of the acid catalyst is desirably 1×10⁻⁴ -5×10⁻¹ mol per molof the hydroxy aromatic compound plus the aldehyde.

Water is usually used as a reaction medium in the condensation reaction.A hydrophilic solvent may be used, however, in case where the hydroxyaromatic compound used is insoluble in an aqueous solution of thealdehyde and the reaction system becomes inhomogeneous at the beginningof the reaction.

The hydrophilic solvent to be used for this purpose may be, forinstance, an alcohol such as methanol, ethanol, propanol, butanol or thelike; a ketone such as acetone, methyl ethyl ketone, methyl isobutylketone or the like; or a cyclic ether such as tetrahydrofurane, dioxaneor the like.

An appropriate amount of the reaction medium to be employed is generally50-1,000 parts by weight per 100 parts by weight of the reaction rawmaterials.

The temperature for the condensation reaction may be suitably determineddepending upon the reactivity of the raw materials, although thetemperature is generally in the range of 10°-150° C., preferably70°-130° C.

The temperature of the system is raised to 130°-230° C. at the finalstage of the condensation reaction in order to eliminate the unreactedmonomers, acid catalyst, and reaction media under a reduced pressure,and to recover the target compound, novolak resin.

Alternatively, the reaction mixture may be dissolved in theabove-mentioned hydrophilic solvent and added to a precipitant such aswater, n-hexane, n-heptane or the like to recover the novolak resin as aprecipitate, which is then separated from the system and dried underheating.

The polystyrene-reduced weight average molecular weight of the novolakresin is usually 200-200,000, preferably 500-100,000, and mostpreferably 600-50,000.

The following polymers and copolymers may be used as examples of thehydroxystyrene resin which is another type of the alkali-soluble resinto be used in this invention: Polymers or copolymers of at least onemonomeric compound selected from hydroxystyrene and derivatives thereof,including hydroxystyrene, α- methyl-m-hydroxystyrene andα-methyl-p-hydroxystyrene; copolymers of hydroxystyrene and/or itsderivative with a vinyl monomer other than hydroxystyrene and itsderivative, said vinyl monomer being, for example, styrene, vinyl ether,acrylonitrile, vinyl chloride, an acrylic acid ester, maleic anhydrideor a vinyl ester of an organic acid; halogenated (iodinated, chlorinatedor brominated) hydroxystyrene polymers or copolymers of at least onemonomeric compound selected from hydroxystyrene and derivatives thereof;and halogenated (iodinated, chlorinated or brominated) copolymers ofhydroxystyrene and/or its derivative with a vinyl monomer other thanhydroxystyrene and its derivative.

Among these, particularly preferable are hydroxystyrene polymer,α-methyl-m-hydroxystyrene polymer, α-methyl-p-hydroxystyrene polymer andthe like.

The hydroxystyrene resin may usually be prepared by conventional anionicpolymerization, cationic polymerization or radical polymerization,though the preparation method is not critical.

The polystyrene-reduced weight average molecular weight of thehydroxystyrene resin is usually 200-200,000, preferably 500-100,000, andmost preferably 600-50,000.

The novolak resin and the hydroxystyrene resin can be employed eitheralone or in combination of two or more. Even other kinds of resins maybe used together with them. In this case, however, it is desirable thatsaid other resins be compatible with the novolak resin and thehydroxystyrene resin. Examples of the combination are a combination of anovolak resin with a hydroxystyrene resin and a combination of a novolakresin with an acrylic or methacrylic acid polymer or copolymer.

Given as examples of the quinonediazide compound to be employed forsynthesizing a condensate with an alkali-soluble resin according to thisinvention are quinonediazidosulfonyl halides, including1,2-naphthoquinonediazidosulfonyl halides, such as1,2-naphthoquinonediazido-4-sulfonyl chloride,1,2-naphthoquinonediazido-5-sulfonyl chloride,1,2-naphthoquinonediazido-6-sulfonyl chloride,1,2-naphthoquinonediazido-4-sulfonyl bromide,1,2-naphthoquinonediazido-5-sulfonyl bromide and1,2-naphthoquinonediazido-6-sulfonyl bormide; and1,2-benzoquinonediazidosulfonyl halides, such as1,2-benzoquinonediazido-4-sulfonyl chloride, 1,2-benzoquinonediazido-4sulfonyl bromide and the like.

These quinonediazide compounds may be used either alone or incombination of two or more.

The condensation ratio of the alkali-soluble resin and thequinonediazide compound is such that the quinonediazido group is presentin a proportion of 1-50% by weight, preferably 1-40% by weight and mostpreferably 1-30% by weight, in the resulting radiation-sensitive resin.If the proportion of quinonediazido group is too small, it is difficultto differentiate the quantity of the silicon compound to be diffused andreacted in the irradiated area and the unirradiated area of the coatedfilm when the condensate is used as a resist for dry development. On theother hand, if the proportion is too large, the substantial portion ofquinonediazido group remains unreacted when irradiated for a shortperiod of time, thus precluding the diffusion and reaction of a siliconcompound at the irradiated areas.

The condensation reaction of an alkali-soluble resin with aquinonediazide compound is carried out in a suitable solvent using abase catalyst.

Given as examples of the solvent used in this reaction are acetone,dioxane, ethyl acetate, propylene glycol monomethyl ether acetate,acetonitrile, methyl ethyl ketone, diisobutyl ketone, methyl isobutylketone, ethylene glycol monomethyl ether acetate, ethylene glycolmonoethyl ether acetate, ethylene glycol monopropyl ether acetate,ethylene glycol monobutyl ether acetate, ethylene glycol monomethylether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether,and ethylene glycol diethyl ether, as well as mixtures of thesesolvents. These solvents are used in an amount usually of 100-10,000parts by weight, preferably 200-3,000 parts by weight, per 100 parts byweight of the alkali-soluble resin plus the quinonediazide compound.

The base catalyst may be an alkali metal salt such as sodiumbicarbonate, sodium carbonate, potassium bicarbonate, potassiumcarbonate or the like, an alkali metal hydroxide such as sodiumhydroxide, potassium hydroxide or the like; an amine such astriethylamine, trimethylamine, triethanolamine, tributylamine,monoethanolamine, pyridine or the like; an ammonium compound such asammonium hydroxide or the like. The base catalyst is used in an amountusually of 0.1-100 parts by weight, preferably 1-50 parts by weight, per100 parts by weight of the alkali-soluble resin plus the quinonediazidecompound.

The condensation reaction is usually conducted at a temperature of10°-50° C., preferably 20°-40° C., and in most cases, the reactioncompletes in 15 minutes--10 hours.

After completion of the reaction, the reaction mixture is put into alarge amount of water, or an acidic aqueous solution containinghydrochloric acid, sulfuric acid or the like to remove the basecatalyst. Alternatively, the base catalyst is eliminated byneutralization and the condensate is recovered as a precipitate.

To 100 parts by weight of this condensate may be added less than 100parts by weight of a quinonediazide compound for forming a mixture withthe alkali-soluble resin as hereinbelow illustrated, or less than 900parts by weight of the alkali-soluble resin.

The quinonediazide compound for forming a mixture with thealkali-soluble resin may be, for example, a (poly)hydroxybenzene such asp-cresol or pyrogallol, a (poly)hydroxyphenyl alkyl ketone such as2,4-dihydroxyphenylpropyl ketone, 2,3,4-trihydroxyphenyl n-hexyl ketone,2,3,4-trihydroxybenzophenone, 2,4,6-trihydroxybenzophenone or2,3,4,4'-tetrahydroxybenzophenone; a quinonediazidosulfonic acid estersuch as an ester of a (poly)hydroxyaryl ketone with1,2-quinonediazido-4-sulfonic acid or 1,2-quinonediazido-5-sulfonicacid; or the like.

Beside these quinonediazide compounds, the quinonediazidosulfonic acidesters mentioned in "Light-Sensitive Systems: by J. Kosar, 339-352(1965), John Wiley & Sons (New York) and "Photoresist" by W. S.DeForest, 50, (1975), McGraw-Hill, Inc., (New York) can be used.

The amount of the quinonediazide compound to be compounded is usually10-50 parts by weight, preferably 15-45 parts by weight, per 100 partsby weight of the alkali-soluble resin.

In this invention, it is desirable to use the condensate of thequinonediazide compound with the alkali-soluble resin as theradiation-sensitive resin.

The photoacid used in this invention means such a compound generating aninorganic or organic acid upon irradiation with ultraviolet light,far-ultraviolet light, X-rays, electron beams, visible light or thelike. Said inorganic acids are, for example, phosphoric acid, iodicacid, hydrogen halides and the like, and said organic acids includesulfonic acids, diazosulfonic acid, nitrobenzylsulfonic acid,cyanobenzylsulfonic acid, nitrobenzylcarboxylic acid,cyanobenzylcarboxylic acid, nitrobenzylphosphoric acid,cyanobenzylphosphoric acid, nitrobenzylnitric acid, cyanobenzylnitricacid and the like. Specific examples of the photoacids are oniums suchas sulfonium, phosphonium, iodonium and diazonium; nitrobenzyl halides;halogenated hydrocarbons; nitrobenzylsulfonic acid esters such as phenylnitrobenzylsulfonate, naphthol nitrobenzylsulfonate, o-nitrobenzyl9,10-diethoxyanthracene-2-sulfonate, p-nitrobenzyl9,10-diethoxyanthracene-2-sulfonate, o-nitrobenzyl9,10-dimethoxyanthracene-2-sulfonate, p-nitrobenzyl9,10-dimethoxyanthracene-2-sulfonate, o-nitrobenzyl9,10-dipropoxyanthracene-2-sulfonate, p-nitrobenzyl9,10-dipropoxyanthracene-2-sulfonate, benzointosylate,2-methylbenzointosylate and the like; cyanobenzylsulfonic acid esterssuch as phenyl cyanobenzylsulfonate and naphthyl cyanobenzylsulfonate;nitrobenzylcarboxylic acid esters such as phenyl nitrobenzylcarboxylateand naphthyl nitrobenzylcarboxylate; cyanobenzylcarboxylic acid esterssuch as phenyl cyanobenzylcarboxylate and naphthylcyanobenzylcarboxylate; nitrobenzylphosphoric acid esters such as phenylnitrobenzylphosphate and naphthyl nitrobenzylphosphate;cyanobenzylphosphoric acid esters such as phenyl cyanobenzylphosphateand naphthyl cyanobenzylphosphate; nitrobenzylnitric acid esters such asphenyl nitrobenzylnitrate and naphthyl nitrobenzylnitrate;cyanobenzylnitric acid esters such as phenyl cyanobenzylnitrate andnaphthyl cyanobenzylnitrate; and the like. Among these, preferred areo-nitrobenzyl 9,10-diethoxyanthracene-2-sulfonate, p-nitrobenzyl9,10-diethoxyanthracene-2-sulfonate, o-nitrobenzyl9,10-dimethoxyanthracene-2-sulfonate, p-nitrobenzyl9,10-dimethoxyanthracene-2-sulfonate, o-nitrobenzyl9,10-dipropoxyanthracene-2-sulfonate, p-nitrobenzyl9,10-dipropoxyanthracene-2-sulfonate, benzointosylate,2-methylbenzointosylate and the like. The amount of the photoacid to beused is usually 0.01-40 parts by weight, preferably 0.1-10 parts byweight, per 100 parts by weight of the radiation-sensitive resin.

A photosensitizer can be added to the radiation-sensitive resincomposition of this invention. The photosensitizers to be employedinclude pyrrole, imidazole, pyrazole, triazole, indole, benzimidazole,benzotriazole, naphthotriazole, dimethyl urea, pyrrolidone, oxyindole,imidazolidone, benzimidazolidone, imidazolidinethione, oxazolidone,benzoxazolidone, pyrazolone, isatin, oxazolidinedione, glutarimide,piperidone, 2H-pirido-[3,2,b][1,4]oxazin-3[4H]one,10H-pirido-[3,2,b][1,4]-benzothiadine, urazol, hydantoin, barbituricacid, glycine, alloxan, and other nitrogen-containing compounds or theirhalogenated derivatives. The amount of the photosensitizer to be used isusually less than 40 parts by weight, preferably 2-10 parts by weight,per 100 parts by weight of the radiation-sensitive resin.

A surfactant may be added to the radiation-sensitive resin compositionof this invention to improve the coating ability such as striation. Thesurfactant to be employed includes nonionic surfactants includingpolyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether,polyoxyethylene stearyl ether and polyoxyethylene oleyl ether,polyoxyethylene alkylphenyl ethers such as polyoxyethylene octylphenylether and polyoxyethylene nonylphenyl ether, polyethylene glycol dialkylesters such as polyethylene glycol dilaurate and polyethylene glycoldistearate; fluorine-containing surfactants containing a fluoroalkyl orperfluoroalkyl group such as Efftop EF301, EF303 and EF352 (manufacturedby Shinakitakasei Co., Ltd.), Megafac F171, F172 and F173 (manufacturedby Dainippon Ink Co., Ltd.), Asahiguard AG710 (manufactured by AsahiGlass Co., Ltd.), Florade FC430 and FC431 (manufactured by Sumitomo 3MCo., Ltd.), and Surflone S-382, SC101, SC102, SC103, SC104, SC105 andSC106 (manufactured by Asahi Glass Co., Ltd.); organosiloxane polymerKP341 (manufactured by Shinetsu Kagaku Kogyo Co., Ltd.); acrylic acid-or methacrylic acid-type polymers and copolymers such as Polyflow No.75, No. 95 and WS (manufactured by Kyoeisha Yushikagaku Kogyo Co.,Ltd.); and the like. The amount of the surfactant to be added is usuallyless than 2 parts by weight, preferably 0.005-1 part by weight, per 100parts by weight of the abovementioned condensate.

In addition, dyes or pigments or adhesion promoters may be further addedto the radiation-sensitive resin composition of this invention so thatpotential images of the irradiated areas can be made visible or adverseeffects by halation during irradiation may be minimized, or in order toimprove the adhesion property of the composition. Dyes which can be usedfor this purpose include oil-soluble dyes, dispersible dyes, basic dyes,methine-type dyes and hydroxyazo-type dyes. More specifically, thesedyes may be Noepengelb 075 (manufactured by BASF A.G.), Neosabongelb 073(ibd.), Solvent Yellow 162, Macrolex Yellow, hydroxyazobenzene and thelike. As examples of the adhesion promoters, silicon compounds such as3-aminopropyltriethoxysilane, vinyltrichlorosilane and2-(3,4-epoxycyclohexylethyl)trimethoxysilane may be given.

Furthermore, antioxydants or defoaming agents can be compounded asrequired to the radiation-sensitive resin composition of this invention.

The radiation-sensitive resin composition according to this inventioncan be prepared by dissolving a radiation-sensitive resin, a photoacidand, as required, various additives, in an organic solvent.

The organic solvents employed for this purpose include glycol etherssuch as ethylene glycol monomethyl ether, diethylene glycol monomethylether, ethylene glycol monoethyl ether, diethylene glycol monoethylether, diethylene glycol dibutyl ether, diethylene glycol dimethylether, propylene glycol monomethyl ether acetate and the like;Cellosolve esters such as methyl Cellosolve acetate, ethyl Cellosolveacetate and butyl Cellosolve acetate; aromatic hydrocarbons such astoluene and xylene; ketones such as methyl ethyl ketone, methyl isobutylketone, cyclohexanone, cyclopentanone, acetonylacetone, acetophenone,isophorone and the like; ethers such as benzyl ethyl ether,1,2-dibutoxyethane and dihexyl ether; fatty acids such as caproic acid,caprylic acid and the like; alcohols such as 1-octanol, 1-nonanol,1-decanol, banzyl alcohol and the like; esters such as ethyl acetate,butyl acetate, isoamyl acetate, 2-ethylhexyl acetate, benzyl acetate,benzyl benzoate, diethyl oxalate, dibutyl oxalate, diethyl malonate,ethyl lactate, methyl lactate, propyl lactate, butyl lactate, dimethylmaleate, diethyl maleate, dibutyl maleate, dibutyl phthalate, dimethylphthalate, ethylene carbonate, propylene carbonate and the like; cycliclactones such as γ-butyrolactone; and urea derivatives such asdimethylimidazolidinone.

These organic solvents may be used alone or in combination of two ormore.

In order to apply the radiation-sensitive resin composition of thisinvention in the form of a resist solution to a substrate, the solutionis dissolved in the above-mentioned organic solvent so that theconcentration of the radiation-sensitive resin composition becomes 5-50%by weight, and the resulting solution is then applied to the substrateby means of spin coating, flow coating or roll coating.

The invention is hereinafter illustrated in more detail by way ofexamples, which should be, by no means, construed as limiting thepresent invention.

EXAMPLE 1

A separable flask equipped with a stirrer, a condenser and a thermometerwas charged with 102 g of phenol, 18 g of t-butylphenol, 92 ml of a 37%aqueous formaldehyde solution and 0.04 g of oxalic acid. The flask wassoaked in an oil bath with stirring and the reaction was conducted at100° C. for 3.5 hours.

Then, the temperature of the oil bath was raised to 180° C., at whichtemperature the internal pressure was reduced to remove water andunreacted phenol, t-butylphenol, formaldehyde and oxalic acid, andrecover the novolak resin.

This novolak resin weighing 25 g and 5 g of1,2-naphthoquinone-(2)-diazo-5-sulfonic acid chloride were dissolved in230 g of acetone. To the solution was added 2.8 g of triethylamine, andthe resulting mixture was subjected to condensation at 40° C. for 1 hourwith stirring. The reaction mixture was then charged dropwise to 5liters of a 0.04% aqueous hydrochloric acid solution to solidify thecondensate.

This condensate was washed with water, dissolved again in 230 g ofacetone, and administered to 5 liters of the same aqueous hydrochloricacid solution to solidify the condensate.

This precipitation of the condensate was repeated three times in total,after which the resin obtained was dried at 40° C. for 48 hours to givethe intended condensate.

Thirty (30) g of this condensate was dissolved in 60 g of ethyleneglycol monoethyl ether acetate, and to this solution was added 1 g ofphenyl nitrobenzylsulfonate. A resist solution was prepared bysubjecting the mixed solution thus obtained to filtration using a 0.2 μmpore size membrane filter. The solution was applied on a silicon waferusing a spinner at a spin speed of 3,000 rpm to form a thin film of a1.7-μm thickness after prebake. The film was dried in a air convectionoven and prebaked at 90° C. for 30 minutes. The silicon wafer wasirradiated with ultraviolet light (g-line) through a reticle patternusing a Nikon NSR-1505 G4D (manufactured by Nippon Kogaku Co., Ltd.).After the irradiation, the silicon wafer was treated withhexamethyldisilazane vapor at 130° C. for 3 minutes.

The silicon wafer thus obtained was placed in a magnetron-enhancedreactive ion etching equipment (ARIES; manufactured by MRC Corp.) andwas developed by oxygen-reactive ion etching to give a resist patternthereon, in which a vertical wall with the minimum line-width of 0.5 μmwas formed in the irradiated area.

COMPARATIVE EXAMPLE 1

A photoresist solution was prepared in the same manner as in Example 1,except that phenyl nitrobenzylsulfonate was not added. The solution wasapplied to a silicon wafer, prebaked, irradiated with ultraviolet light,treated with hexamethyldisilazane vapor and developed by oxygen-reactiveion etching. Areas not irradiated with ultraviolet light remained on thesurface, failing to obtain a resist pattern.

EXAMPLE 2

In 60 g of ethylene glycol monoethyl ether acetate was dissolved 30 g ofa condensate of 1,2-naphthoquinone-(2)-diazo-5-sulfonic chloride with anovolak resin synthesized in the same manner as in Example 1, and to theresulting solution was added 0.9 g of p-nitrobenzyl9,10-diethoxyanthracene-2-sulfonate. The resulting mixture was filteredthrough a mambrane filter having a pore diameter of 0.2 μm to prepare aresist solution.

In the same manner as in Example 1, this resist solution was applied ona silicon wafer, prebaked, irradiated with ultraviolet light, treatedwith hexamethyldisilazane vapor and then developed by oxygen-reactiveion etching, thereby obtaining a resist pattern in which a vertical wallwith the minimum line-width of 0.5 μm was formed in the irradiated area.Also, the thickness of the resist pattern was 95% based on that beforeirradiation.

The radiation-sensitive (resin) composition of this invention, when usedas a resist for dry development, promotes diffusion and reaction of asilicon compound selectively at irradiated areas, due to presence of anacid which is generated upon irradiation. This brings about a highdegree of resolution and selectivity of etching, and provides an etchingimage at high precision and with excellent reproducibility.

The present composition, therefore, is capable of increasing integrationof semiconductor elements such as ICs and promoting the device yield.

What is claimed is:
 1. A radiation-sensitive resin compositioncomprising in admixture a quinonediazide-type radiation-sensitive resinwherein the quinonediazide-type radiation-sensitive resin is at leastone member selected from the group consisting of a condensate of aquinonediazide compound with an alkali-soluble resin and a mixture of aquinonediazide compound and an alkali-soluble resin and as a compoundgenerating an acid upon irradiation a member selected from the groupconsisting of nitrobenzylsulfonic acid esters, cyanobenzylsulfonic acidesters, nitrobenzylcarboxylic acid esters, nitrobenzylphosphoric acidesters, nitrobenzylnitric acid esters and cyanobenzylnitric acid esters;said radiation-sensitive resin and said compound generating an acidbeing present in an amount effective to provide a photosensitive resistpattern.
 2. The radiation-sensitive resin composition according to claim1, wherein the alkali-soluble resin is at least one member selected fromthe group consisting of a novolak resin having hydroxyl groups and ahydroxystyrene resin.
 3. The radiation-sensitive resin compositionaccording to claim 2, wherein the hydroxystyrene resin is at least onemember selected from the group consisting of halogenated orunhalogenated polymers and copolymers of at least one compound selectedfrom hydroxystyrene and derivatives thereof and copolymers of at leastone compound selected from hydroxystyrene and its derivatives with atleast one other vinyl monomer.
 4. The radiation-sensitive resincomposition according to claim 3, wherein the derivatives ofhydroxystyrene include α-methyl-m-hydroxystyrene andα-methyl-p-hydroxystyrene and the at least one other vinyl monomer isselected from the group consisting of styrene, vinyl ether,acrylonitrile, vinyl chloride, acrylic acid esters, maleic anhydride andvinyl esters of organic acids.
 5. The radiation-sensitive resincomposition according to claim 2, wherein the hydroxystyrene resin is ahydroxystyrene polymer, α-methyl-m-hydroxystyrene polymer orβ-methyl-p-hydroxystyrene polymer.
 6. The radiation-sensitive resincomposition according to claim 1, wherein the quinonediazide compound tobe condensed with the alkali-soluble resin is selected from the groupconsisting of 1,2-naphthoquinonediazido-4-sulfonyl chloride,1,2-naphthoquinonediazido-5-sulfonyl chloride,1,2-naphthoquinonediazido-6-sulfonyl chloride,1,2-naphthoquinonediazido-4-sulfonyl bromide,1,2-naphthoquinonediazido-5-sulfonyl bromide,1,2-naphthoquinonediazido-6-sulfonyl bromide,1,2-benzoquinonediazido-4-sulfonyl chloride and1,2-benzoquinonediazido-4-sulfonyl bromide.
 7. The radiation-sensitiveresin composition according to claim 1, wherein the condensation ratioof the alkali-soluble resin and the quinonediazide compound is such thatthe quinonediazido group is present in a proportion of 1-50% by weightin the resulting radiation sensitive resin.
 8. The radiation-sensitiveresin composition according to claim 1, wherein the quinonediazidecompound to be mixed with the alkali-soluble resin is selected from thegroup consisting of condensates of (poly)hydroxybenzenes,(poly)hydroxyphenyl alkyl ketones and quinonediazidosulfonic acid esterswith 1,2-quinonediazido-4-sulfonic acid or 1,2-quinonediazido-5-sulfonicacid.
 9. The radiation-sensitive resin composition according to claim 1,wherein the amount of the quinonediazide compound to be mixed with thealkali-soluble resin is 10-50 parts by weight per 100 parts by weight ofthe alkali-solible resin.
 10. The radiation-sensitive resin compositionaccording to claim 1, wherein the nitrobenzylsulfonic acid estersinclude o-nitrobenzyl 9,10-diethoxyanthracene-2-sulfonate, p-nitrobenzyl9,10-diethoxyanthracene-2-sulfonate, o-nitrobenzyl9,10-dimethoxyanthracene-2-sulfonate, p-nitrobenzyl9,10-dimethoxyanthracene-2-sulfonate, o-nitrobenzyl9,10-dipropoxyanthracene-2-sulfonate, p-nitrobenzyl9,10-dipropoxyanthracene-2-sulfonate, benzointosylate and2-methylbenzointosylate.
 11. The radiation-sensitive resin compositionaccording to claim 1, wherein the compound generating an acid uponirradiation is contained in an amount of 0.01-40 parts by weight per 100parts by weight of the quinonediazide-type radiation-sensitive resin.12. The composition according to claim 1 wherein the compound generatingan acid upon irradiation is a nitrobenzylsulfonic acid ester.